Based on Sister of the Road, the fictionalized autobiography of radical and transient Bertha Thompson as written by physician Dr. Ben L. Reitman, Boxcar Bertha Thompson, a woman labor organizer in Arkansas during the violence-filled Depression of the early 30 s meets up with rabble-rousing union man Big Bill Shelly and they team up to fight the corrupt railroad establishment and she is eventually sucked into a life of crime with him.